1. Field of the Invention
The present invention relates to a current collector for a molten salt battery, a process for producing a current collector material for the above current collector and a molten salt battery using the above current collector.
2. Description of Related Art
A molten salt battery in which liquid sodium is used as an anode active material, has such characteristics as (1) high energy density and (2) no self-discharge as compared with other secondary batteries, and has been expected-to have a usefulness as a battery for electric vehicle or a power storage battery.
The above molten salt battery comprises several parts. A current collector, which is used as one of the parts and plays a role of feeding an electron to an active material, has heretofore been produced by, for example, a method of bonding a porous carbon material to graphite, a method of bonding a porous carbon material to a vitreous carbon, or a method of bonding a porous carbon material to tungsten.
However, the current collector produced by the method of bonding a porous carbon material to graphite, has such problems that the graphite easily forms, during charging, an intercalation compound with a molten salt used as an electrolyte, this intercalation compound causes the expansion and shrinkage of the graphite, and finally, the current collector collapses. The current collector produced by the method of bonding a porous carbon material to a vitreous carbon forms no intercalation compound with the molten salt but has such a problem that since its electrical resistance is high, the battery resistance increases. The current collector produced by the method of bonding a porous carbon material to tungsten has such a problem that use of tungsten makes high the raw material cost and the processing cost. Therefore, these problems of the current collectors produced by the conventional methods result in a battery of high cost, low capacity and/or high internal resistance. Therefore, it has been desired to solve the above problems.